1. Field of the Invention
The present invention relates to a device and a method for separating a filter ring component from a fluid-holding reservoir component of a funnel with minimal operator effort.
2. Description of the Background Art
In certain sterile operations (e.g., laboratory and manufacturing procedures), it is necessary to regularly monitor fluid supplies, such as water supplies, used in such procedures to ensure that they do not contain unacceptable levels of contaminants, such as biological contaminants. Typical biological contaminants include bacteria and fungi. One method of monitoring fluid supplies involves passing a specified sample volume of a fluid from a fluid supply through a filter, positioning the filter on a contained biological growth medium (e.g., an agar plate), enclosing and incubating the contained biological growth medium, and then observing the level of the biological growth at prescribed intervals of time. Specialized filtration testing systems are manufactured for this purpose.
One such filtration testing system is illustrated in FIGS. 1-3. This filtration testing system 60 includes a funnel 10 that includes a fluid-holding cup 12 for receiving an amount of a fluid to be tested and a filter ring 20 having a filter 26 (e.g., a filtration mesh) disposed across its opening. More specifically, the cup 12 includes a top end 14, a bottom end 16 having a width (e.g., diameter) less than that of the top end 14, and a frusto-conical section 18. The filter ring 20 includes a wide portion 22 and a narrow portion 24 having a width (e.g., diameter) less than that of the wide portion 22. The filter 26 is disposed generally between the wide portion 22 and the narrow portion 24. The filter ring 20 is frangibly attached, at frangible connection 28, to the bottom end 16 of the cup 12. The frangible connection 28 is constructed and arranged to break upon application to the funnel 10 of a sufficient compressive axial force, thereby permitting the narrow section 24 of the filter ring to collapse into the bottom end 16 of the cup 12. After the frangible connection 28 is broken, the filter ring 20 and cup 12 can be separated from each other.
The system 60 further includes a growth medium plate 30 (e.g., an open-ended agar plate), a lower cover plate 40, and an upper cover plate 50.
The filter ring 20 can be connected to the growth medium plate 30. The growth medium plate 30 has a size and shape that conforms to the interior of the wide portion 22 of the filter ring 20, permitting the plate 30 to be snugly inserted into the wide portion 22 as shown FIG. 3. The growth medium plate 30 includes a layer of growth medium 32 supported by a lattice structure 34. An inner extension 36 is preferably circular and projects away from the growth medium 32 and lattice structure 34, generally encircling the growth medium 32 and the lattice structure 34.
The lower cover plate 40 has a size and shape that conforms to the interior of the growth medium plate 30, permitting the lower cover plate 40 to be snugly inserted into the growth medium plate 30 as shown FIG. 3. When the lower cover plate 40 is inserted into the plate 30, a top surface 42 of the lower cover plate 40 makes contact with the inner extension 36, thereby forming a partial enclosure surrounding the growth medium 32 and the lattice structure 34.
The upper cover plate 50 includes a first extension 52 and a second extension 54. The first extension 52 has a size and shape that permits that upper cover plate 50 to be secured to the top end 14 of cup 12 by inserting the first extension 52 into the cup 12. After the cup 12 and the filter ring 20 have been separated from each other, the second extension 54 has a size and shape that permits the upper cover plate 50 to be secured to the narrow portion 24 of the filter ring 20 by inserting the second extension 54 into the narrow portion 24.
The funnel 10, in combination with the growth medium plate 30, the upper cover plate 50, and the lower cover plate 40, make up the fluid contamination detection system 60 having an overall axial length L. A suitable system of the type shown in FIGS. 1-3 is the Milliflex™ HAWG 0.45 μM, sterilized filtration funnel available from the Millipore Corporation, Bedford, Mass. (Cat. No. MXHAWG124). This system may further include, for example, a Prefilled Milliflex™ Cassette containing tryptic soy agar available from the Millipore Corporation (Cat. No. MXSMCTS48).
In a conventional fluid contamination detection system and procedure, the funnel 10 is placed on a suction mechanism, or vacuum suction, (such as the Milliflex™ Sensor II automatic vacuum available from the Millipore Corporation (Cat. No. MXP520015)), a prescribed volume of fluid (e.g., about 10 mL) is then poured into the cup 12, and the fluid contents of the cup 12 are drawn through the filter 26 of the filter ring 20. After the fluid has been drawn through the filter 26, the growth medium plate 30 is joined to the filter ring 20 so that the growth medium 32 contained within the growth medium plate 30 contacts the filter 26 of the filter ring 20. Thereafter, the filter ring 20 and growth medium plate 30 are separated from the cup 12. To separate the filter ring 20 and growth medium plate 30 combination from the cup 12, the filter 10 and growth medium plate 30 are manually squeezed between the palms and fingers of an operator's hands to apply an axial compressive force to the filter 10 and growth medium plate 30 that is sufficient to break the frangible connection 28 joining the cup 12 and ring 20 so that the narrow portion 24 of the filter ring 20 collapses into the bottom end 16 of the cup 12. The filter ring 20 and growth medium plate 30 are then separated from the cup 12, and the upper cover plate 50 is joined to the open end of the filter ring 20 before incubating the enclosed growth medium plate 30 at a temperature of about 37° C.
It is generally desirable to perform this procedure in a laminar flow hood in order to limit exposure of the filter to airborne contaminants that could interfere with fluid monitoring test results. During the incubation phase, the growth medium plate 30 is examined at prescribed time intervals, e.g., 24, 48, and 72 hours, and the number of colonies that have formed on the plate (the bioburden) is determined. Such a fluid contamination detection system is especially important for the clinical diagnostics industry, where the presence of biological contaminants in fluids used to manufacture reagents for commercial test kits could affect the results of assays performed using those test kits.
A problem with the fluid contamination detection system and procedure described above is that laboratory and manufacturing facilities might have to perform dozens of fluid contamination detection tests in a day. As a consequence, an operator may be required to repeatedly apply a manual force with their hands to separate filter ring 20 and growth medium plate 30 combinations from corresponding cups 12, often resulting in discomfort to the operator's hands or, more seriously, causing repetitive stress injuries, such as carpal tunnel syndrome. Accordingly, there is a need for a device and method that overcome the problems associated with isolating filter ring 20 and growth medium plate 30 combinations in traditional detection systems.